FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT
As known in the prior art, in connection with the wet end fabrics of a paper machine, for example, in guiding, spreading and cleaning of a felt in a press section, a separate device is used for each purpose, at least one of each of them being arranged for said purpose in connection with each fabric. In the arrangements known in the state of the art, the devices used for these purposes are an automatic guide, a manual guide, a guide roll, a curved spreader roll, suction units and jets. Such separate devices cause extra costs, they take space and require support structures in connection with the frame structures of the machine.
One problem with the suction units used in connection with the separate devices known in the prior art has been that the width of the suction slot has not always been adjustable so that several suction units may have been needed for each felt.
One problem in connection with suction units has also been that the suction unit rubs against the felt so that the press section consumes more power.
In the arrangements known in the state of the art, in fast machines in particular, the felt has worn quickly, which has been partly due to the rubbing of the ceramic covers of felt suction units. Rolls and mechanical impurities also wear felt.
The spreader rolls in the arrangements known in the prior art have had a constant curvature, and thus it has not been possible to adjust their spreading effect.
An object of the invention is to provide a device in which the above-noted problems with the prior art devices are not encountered.
An object of the invention is also to provide a device which is of low cost.
One further non-indispensable object of the invention is also to disclose a device in which the width of the suction slot in the suction unit is adjustable.
One further non-indispensable object of the invention is also to disclose a device in which the curvature of the spreader roll can be adjusted.
In accordance with the invention, the device comprises device components that accomplish at least two of the following functions: guiding, spreading and/or cleaning of a fabric. An advantageous embodiment example of the invention comprises the above-mentioned functions, all in the same device.
The device according to the invention thus comprises in accordance with an advantageous embodiment an automatic guide, a guide roll, a curved spreader roll and a suction unit in a single device assembly. Jets may also be incorporated in the device assembly.
In accordance with an advantageous additional feature of the invention, instead of prior known ceramic ribs, suction ribs that can be bent, for example, plastic ribs or equivalent are used as suction ribs of the suction slot of the suction unit, which is possible because the fabric is supported by rollers in the device. The adjustment of plastic ribs for regulating the width of the suction slot is easy to carry out and, when needed, the suction width can be increased, for example, at the edges with respect to the centre because the plastic rib is easy to bend.
Advantageously, in accordance with an additional feature of the device according to the invention, the journalling of the rollers (the guide roll and the spreader roll are formed of rollers) is accomplished by means of bearings lubricated with circulating grease or circulating oil or by means of permanently lubricated bearings, and the device can be turned upside down by using a hydraulic motor or cylinder for the purpose of cleaning. Advantageously, the end seals of the suction slot in the suction unit of the device are accomplished, for example, by means of adjustable overlapping joints. The suction pipe system of the suction unit is laid from both the driving side and the tending side, thus achieving a good and uniform suction effect.
The functions of the curved spreader roll are provided by placing the rollers forming the spreader roll in a form which is suitably curved. In a press section, the deflections of tubular rolls can be compensated for, for example, by placing the rollers at the edges of the machine at different heights using, for example, spacer plates under the bearing housings.
In felt guidance, the manual guide of the prior art arrangements has been omitted and the automatic guide is most preferably accomplished as a mechanical guide comprising linear guides and a worm gear, whereby the problems of known devices are avoided. The automatic guide is provided with such a movement length that no separate manual guide is needed. The movement length is, for example, 140 mm. In connection with the device in accordance with the invention, as a measuring head is advantageously used a non-contacting sensor or a contacting measuring transducer, i.e. a felt and wire tracking device.
The invention provides substantial savings in costs as the space requirement and the complexity of the device assembly are reduced. When used on fast machines, the service life of the fabric increases if the wear of the felt loop constitutes the main reason for replacement of the felt. The other main reasons for replacement of the felt include, for example, hardening, clogging, contamination or scheduled shutdown.
Only one device according to the invention is needed for each fabric because the width of the suction slot of the suction unit part can be adjusted, which allows optimization to be accomplished for each individual felt.
The power consumption of the press is reduced because the suction unit is less rubbing and fewer rolls are used than in the prior art arrangements since separate guide rolls and spreader rolls are no longer needed as they have been formed of rollers in connection with the device.
Curvature, i.e the power of spreading, can be regulated, in which connection the spreading effect can be regulated, and automatic control is self retaining retaining owing to a trapezoid-thread screw used in accordance with an advantageous example. It is easy to add automation to the device according to the invention, for example, controls and their automation can be readily incorporated, which increases the means of affecting the felt loop, for example, the profiling of the moisture of the felt by adjusting the width of the suction slot.